The present invention relates in general to an electrical method and apparatus for preventing biofouling buildup on surfaces exposed to fresh water or saltwater.
The growth and accumulation of biological organisms and the by-products resulting therefrom on surfaces of structures and machinery in contact with either fresh water or salt water, represents a constant maintenance problem for such structures and machinery. For example, the hull of ships and associated seawater exposed systems become coated with both microfouling and macrofouling material such as water-borne algae, bacterial-induced biofilm, barnacles, mussels, etc., which may additionally enhance or induce corrosion.
In order to deal with the foregoing problem, a considerable amount of research activity has been undertaken in an effort to find solutions that are both economical and environmentally compatible, involving various non-chemical treatment technologies including sonics. Biofouling control by use of sonics under study for some time, is now well known and includes the use of conventional ultrasonic sources found to have mixed results for a variety of reasons, including for example a low cavitation threshold at ultrasonic frequencies associated with the use of prior biofouling treating techniques. The use of electric fields and currents in biofouling control applications are also known, but has met with varied results which are furthermore difficult to duplicate.
In connection with the foregoing referred to technologies, U.S. Pat. Nos. 3,486,062, 5,208,788 and 5,245,988 to Schrom, Dancer et al. and Einars et al., respectively, may be of interest. The Schrom patent relates to the generation of shock waves by electric spark discharge from an electrode in a surrounding liquid medium, such shock waves being directed and focused for various types of manufacturing and process operations. The Dancer et al. patent relates to circuitry for triggering sparks within gaps between electrodes for purpose of electrode position detection and correction. As to the Einars et al. patent, it relates to the production of shock waves by electrical discharge of capacitor stored energy between electrodes immersed in liquid for treatment of living tissue. However, none of the foregoing Schrom, Dancer et al. and Einars et al. patents relates to biofouling prevention, treatment or control.
Accordingly, it is an important object of the present invention to generate pulsed acoustic shock waves for continuous biofouling control purposes within a body of liquid water, with greater efficiency in the delivery of acoustic power and having a higher cavitation threshold to enlarge the water treatment region with reduced collateral damage.